Improvement Of Rice Grain Quality By Using CRISPR/Cas9 System

Rice is one of the most important food crops in China,and its high yield is closely related to national food security and people's lives.With the improvement of living standards,people are no longer just satisfied with solving the problem of food and clothing,and the requirements for the quality of rice are increasing.This prompts scientists to pay more and more attentions to the quality of rice in China.Rice quality mainly includes four aspects:grinding quality,appearance quality,cooking and eating quality and nutritional quality.In recent years,with the rapid development of rice functional genomics and sequencing technology,great progress has been made in the study of rice quality related genes,and a series of functional markers have been developed for the cultivation of high-quality rice varieties.With the continuous development and improvement of technology,molecular marker-assisted selection(MAS),gene editing and other technologies are also increasingly used in the research and cultivation of high-quality rice varieties.In this study,three vectors for SSSII-2,BADH2,GS9 and Wx genes were constructed to improve rice quality using CRISPR/Cas9 gene editing technology.And different mutants were obtained,The target gene expression,physicochemical properties and agronomic traits of the transgenic rice were analyzed.The main results are as follows:1.Successfully construct three kind vectors:pB-SSSII-2/BADH2,pB-GS9/BADH2AVx and pCXUN-BE3-Wx,and the target fragment was transfered into the recipient parents.2.Real-time PCR analysis showed that the expression of the target genes in the transgenic seeds was significantly reduced compaired to that of the untransformed control.3.The amylose content and gel consistency of SSSII-2 transformants had no significant change compared with the recipient parents.The amylose content of Wx transformants was significantly lower than that of the recipient parent,and the gel consistency was significantly higher than that of the recipient parent,indicating that the rice quality of the transgenic rice became soft.4.The results of starch viscosity analysis showed that the gelatinization temperature of transgenic rice was lower than that of the recipient parent,and the BDV was increased relative to the parent.The SBV and the CSV decreased compared to the parent.These changes indicate that the rice quality is softer than the parent,indicating that the taste quality of the transgenic lines is improved.5.Editing of BADH2 using CRISPR/Cas9 gene editing technology results aroma to transgenic rice.6.There was no significant change in plant height and shape of transgenic rice.The seed chalkines of each line of the Wx transgenic lines mediated with the pB-GS9/BADH2/Wx vector was very high,and the seed chalkines of the transgenic lines mediated with other two vectors was very low,which was consistent with the recipient parent.The grain length of the GS9 transgenic lines was increased significantly,while the grain width showed a significant decrease,and the grain thickness was significantly reduced.The 100-grain weight of the transgenic lines was decreased.